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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 20 |
| 7 | 82 |
| 8 | 376 |
| 9 | 2010 |
| 10 | 11788 |
| 11 | 77816 |
| 12 | 556016 |
| 13 | 4366814 |
| 14 | 36773666 |
| 15 | 335394762 |
| 16 | 3251474116 |
| 17 | 33770466316 |
| 18 | 370474881290 |
| 19 | 4317182375632 |
| 20 | 52861107601060 |
| 21 | 683129289079532 |
| 22 | 9234228045432682 |
| 23 | 131059243976153410 |
[1,1,1,2,6,20,82,376,2010,11788,77816,556016, 4366814,36773666,335394762,3251474116,33770466316, 370474881290,4317182375632,52861107601060, 683129289079532,9234228045432682, 131059243976153410] |